Effects of Acrylic Restorations on the of Monkeys

CARLOS E. NASJLETI, WALTER A. CASTELLI, and BENJAMIN E. KELLER Veterans Administration Hospital and the University of Michigan, Ann Arbor, Michigan 48105, USA

Replanted teeth that had an acrylic restora- implanted acrylic teeth. Similar results tion in the middle third of their roots were were obtained by Tobin-White,9 who placed studied from three days to six months after acrylic teeth into sockets in which fluid grafting. The study revealed that the acrylic acrylic resin had been introduced before po- obturator elicited epithelial proliferation, sitioning the implants. These conflicting re- fibrous encapsulation, moderate chronic in- ports indicated a necessity for further flammation, and adjacent alveolar loss. investigation. We thought that the histo- pathologic condition of the periodontium in Data dealing with successful or unsuccessful relation to the acrylic restoration must be acrylic implants have accumulated delineated clearly. gradually during the past 20 years. Flohr' The present study is a histological exam- studied plastic material as a possible sub- ination of the periodontium of replanted stitute for natural teeth by placing screw-type teeth that had an acrylic restoration in the acrylic roots into surgically created alveolar middle third of their roots. The study was sockets. He reported that normal connective done from three days to six months after tissue formed against the acrylic, and only grafting. With this model, observations of minimal infiltration occurred. Hodosh, et the periodontal tissue reaction around ce- al24 reported a high degree of success with mentum and the acrylic restoration could be acrylic implants in man, baboons, and dogs. compared. Success was measured by the firmness and stability of the implants, by their ability to Materials and Methods stand up under the stress of mastication, and Nine healthy male rhesus monkeys by the absence of gross gingival and perio- (Macaca mulatta) were used for this study. dontal diseases. Brown, Neff, and Tylenda5 All the monkeys were adults and were ap- reported encouraging results in a preliminary proximately the same size and weight. A step study of acrylic tooth implants in monkeys. by step sequence of the methods used was On the other hand, Waerhaug and Zander6 reported recently.10 Briefly, after extraction, demonstrated that acrylic resin implants ex- the left central maxillary incisors were erted little or no irritation on hard and soft treated endodontically with zinc oxide- tissues, but concluded that the life of the eugenol paste and gutta-percha points, and acrylic implant is limited and that it is prob- a cavity was prepared in the distal aspect ably of no practical value. Narang and of the middle third of the roots. The pre- Wells7 reported that efforts to achieve long- pared cavity was filled with a cold-curing term maintenance of acrylic tooth implants acrylic resin* and after four minutes setting have achieved only limited success. Failures time, the tooth was replanted. For stabiliza- were characterized by gingival inflammation, tion, the replants were sprinted by cementing alveolar bone loss, and excessive mobility of a common metal inlay into previously pre- the acrylic tooth implants. In spite of careful pared cavities of the central incisors. After splinting, Iwaschenko8 found epithelial pro- surgery, the monkeys were given 100 mg liferation and subsequent exfoliation of the * Sevriton, Amalgamated Dental Trade Dist., Ltd., Received for publication June 24, 1971. London, Eng. 1382 I'ol .5 No}. 5 ACRYL[IC RFS7 ORATIONS & THE IPERIODONTIUM 1383

FIG 1. Twenty one days after tooth replantation. Dense band of transseptal periodontal fibers extends from cernentum of replanted tooth (re) to cementLum of control untreated tooth (co) over crest of alveolar bone septum (HL&E stain; orig mag X45, reproduced at 78%). oxytetracycline dissolved in 16 ounces of ment and the intense leukocytic infiltration, water daily and were maintained on a soft the original outline was diet for the first week. The monkeys were preserved without noticeable sloughing. By killed postoperatively at 3, 6, 21, and 30 six days, the crevicu~lar epithelium was re- days, and at three, four, and six months. The attached at the cementoenamel junction, and involved teeth with surrounding bone and further repair was observed by proliferation soft tissue were excised in block sections. of epithelial cells, which quantitatively re- These sections were fixed in 10% buffered stored the thickness of the tissue in that Formalin solution, and were decalcified in region. The blood clot in this specimen was either formic or nitric acid. Acrylic restora- replaced partially by loose fibrillar tissue, tions were dissolved in chloroform for four and at the periphery of the clot there was hours. Serial sections of the decalcified, evidence of vascular proliferation. Lympho- paraffin-embedded tissues were sectioned in cytic and histocytic inflammatory cells be- the mesial-distal direction, and stained with came prominent along the replanted root. hematoxylin and eosin (H&E) and Mal- The collagen fibers of the periodontal mem- lory's periodic acid-Schiff (PAS) stain, for brane demonstrated increased cellularity, histological examination. and a definite tendency toward orientation. In the middle third of the root, adjacent Results to the acrylic obturator, a trace of a thin Histological sections of the three day post- zone of parallel collagen fibers with inter- operative specimen disclosed a broad zone of spersed leukocytes was seen. Between this fibrin clot, which was undergoing organiza- zone and the interdental septum of the tion. Despite the lack of epithelial reattach- alveolar bone, the connective tissue seemed slightly edematous and periodontal fibers ap-

* Cosa Terramycin, Pfizer & Co., Inc., New York, peared somewhat disoriented. Healing in the NY. 21-day specimen was advanced considerably 1384 NASJLETI, CASTE! LI, AND KElLER I Dent Res Septeinher-October .1972 over that observed in the six-(lay specimen. The subgingival connective tissue was in- filtrated moderately with chronic inflamma- tory cells, and a dense band of transseptal periodontal fibers extended from the cemen- turn of one incisor to the of the adjacent incisor over the crest of the interdental septum of alveolar bone (Fig 1). At the acrylic site there was a notable zone of moderate round cell infiltration, fibrosis, and fatty tissue, as well as hyalin, degeneration. Coarse connective tissue fibers were aligned parallel to the acrylic cavity. When the apical portion of the root was scanned, fibroblastic and osteoblastic ac- tivity was evident, and cemental resorption and dentoalveolar ankylosis were a common finding.

FIG 3.- Area between cervical third and acrylic third of root of a 30-day specimen. Note fibrous components of encapsulated zone attaching to root cement-lum. re, Replanted tooth; e, epithelial proliferation (H&E stain; orig mag x250, reproduced at 56%).

Three specimens were available for a 30- day postoperative evaluation. In every in- stance, the cervical third of the root showed a decrease in the cellularity of the perio- dontal membrane. Occasionally, epithelial rests of Malassez and pools of fibrillar ma- terial without definite arrangements were noted. In all three specimens, tissue elements adjacent to the acrylic cavity showed the following features: (1) An epithelial pro- liferation extended over the whole acrylic wall (Fig 2); however, this epithelial prolif- eration was not connected with the crevicu- lar epithelium. This epithelial proliferation appeared to form a protective barrier be- tween the acrylic obturator and the adjacent FIG 2.-Acrylic site of a 30-day replanted tooth. Polymer elicited epithelial proliferation connective tissue fibers. (2) In the perio- (e), fibrous encapsulation (c), and chronic dontal space and covering the epithelial pro- inflammation (ch) (H&E stain; orig mag X250, liferation, the acrylic restoration also elicited reproduced at 67%). the formation of a fibrous encapsulation. Vol 51 No. 5 ACRYLIC RESTORATIONS & THE PERIODONTIUM 1385

The fibers forming this encapsulated zone dontal membrane to become reestablished were parallel to the epithelial proliferation as after replantation. In their work, dento- well as to the acrylic cavity, which denotes alveolar ankylosis was not observed; and, a nonfunctional orientation. The fibrous without exception, connective tissue filled components of the encapsulated zone were the space between the transplanted root and attached to the cementum root surface (Fig the alveolar bone. 3). (3) A chronic inflammatory reaction In the present study half of the tooth re- was present in the epithelial proliferation plants showed dentoalveolar ankylosis, layer and in the fibrous encapsulation layer. whereas the other half did not show dento- There was a moderate number of foreign alveolar ankylosis. The cause for these differ- body cells, macrophages, lymphocytes, and ent responses could not be determined. In polymorphonuclear leucocytes (Fig 2). (4) the present study, such factors as exodontia, A notable decrease in osteoblastic activity at as well as overmanipulation during root the mesial margins of the interdental sep- canal therapy and acrylic cavity preparation, tums and a somewhat granular appearance may account for the response of the teeth of the bone was observed. In addition, the that resulted in dentoalveolar ankylosis. amount of osteoid was decreased locally. In Hammer18 suggested that the centers of re- the apical third of the root, the specimens sorption and apposition in replanted teeth showed dentoalveolar ankylosis with a de- would lend themselves to ankylosis. In his crease in fibroblastic activity. opinion, resorption starts where the perio- Three months after surgery, the replanted dontal membrane is damaged during tooth tooth showed an intense, progressive, osteo- extraction, and it may be that these regions blastic activity around the apical half of the give rise to ankylosis. Tooth replants demon- root. The periodontal space was interrupted strating an absence of ankylosis had func- by sporadic regions of bony ankylosis as- tional periodontal fibers supporting the tooth sociated with cemental resorption and ce- and attaching to both the alveolar bone and mental deposition. However, at the acrylic cementum. In addition, small regions of pre- site a rapid fibroblastic proliferation was vious root resorption had been repaired by noted in the fibrous capsule; it also appeared new cementum. to infiltrate the adjacent bone and dentin. Previously, Hodosh and associates2-4 Details of this nonmalignant lesion were re- used exact replicas of natural teeth fabri- ported recently.'0 cated of heat-cured acrylic resin, and The four- and six-month specimens had a reported that the fibers in the periodontal normal periodontal membrane over the ma- membrane surrounding the acrylic tooth im- jor portion of the replanted root surfaces; plant tended to run in a more vertical however, there was invariably induction of orientation; that these fibers inserted directly epithelial proliferation, fibrous encapsula- into the acrylic resin; and, that the sur- tion, chronic inflammation, and osteoblastic rounding alveolar bone had osteoblastic activity at the acrylic site. In contrast to the activity along the periodontal membrane sur- earlier replants, the four- and six-month face. Contrary to these findings, the present specimens did not show dentoalveolar anky- study revealed that the acrylic obturator losis, and regions of cemental resorption had elicited epithelial proliferation, fibrous en- been repaired by extensive deposits of new capsulation, chronic inflammation, and a cementum. decrease in osteoblastic activity of the ad- jacent alveolar bone septums. The factors Discussion responsible for these reactions in our study There seems to be no disagreement as to are still unclear. Since we used cold-cured the necessity of replacing the pulp with a acrylic resin, which is polymerized at room proper filling before tooth replantation,11-13 temperature, there could be a possibility of as well as to replanting teeth with the orig- incomplete polymerization that left mono- inal periodontal fibers attached.14-16 Loe and mers present which may have caused the Waerhaug'7 conducted long-term experi- observed tissue responses. However, Waer- ments in which they intentionally replanted haug and Lbel9 concluded that there was no teeth in dogs and monkeys; their studies basic difference in the tissue reaction to showed that it is possible for a normal perio- cold-cured and heat-cured acrylic resins. 1386 NASJLETI, CASTELLI, AND KELLER J Dent Res September-October 1972 Our findings are consistent with, and help replace human or animal tissues has been to explain, earlier reports of acrylic tooth provocative, often discouraging, and never implant failures as reported by Waerhaug without debate. It is clear why dental in- and Zander,6 Narang and Wells,7 Iwas- vestigators have sought a material like chenko,8 and Tobin-White,9 among others. acrylic resin to replace natural teeth. The These investigators explored acrylic tooth appeal of acrylic resins is apparent because implants as a possible substitute for natural such polymers are available in unlimited teeth and found that some of their tooth quantities, and they are relatively inexpen- implants showed gingival inflammation, sive to produce. Further, the acrylic tooth alveolar bone loss, epithelial proliferation, or may be made in the desired size, shape, and exfoliated teeth. It should be noted that, in color. However, to date, there is serious Cserepfalvi's opinion,20 the experiments with doubt as to whether acrylic tooth implants artificial implants are certain to lead to fail- have survived in toto.6-9 ure because they are contrary to the biologic principle that no living tissue can survive, Conclusions without ill effect, any long lasting pressure The purpose of the present study was to that exceeds the capillary pressure. Further- examine the periodontium of replanted more, Orban21 has suggested that reattach- teeth that had a cold-cured acrylic obturator ment of periodontal fibers can "only be a in their roots. Periodontal tissue reaction reattachment of connective tissue . . . when, around root cementum and the acrylic connective tissue comes into contact with restoration were compared. cementum root surface." The study showed that it is possible for a More important, the current debate is normal periodontal membrane to become focused on reports of successful acrylic tooth reestablished after tooth replantation. How- implants in human beings,24 in spite of the ever, the acrylic restoration elicited epithelial evidence which contraindicates the use of proliferation, fibrous encapsulation, chronic acrylic implants in man.22-25 Experimental inflammation, and alveolar bone loss. These work with rats by Oppenheimer and asso- findings are in accord, and help to explain, ciates22 has shown that acrylic resin em- earlier reports of acrylic tooth implant fail- bedded subcutaneously for approximately ures that included gingival inflammation, one year in film or sheet form induced epithelial proliferation, alveolar bone loss, sarcomas in significant numbers, up to 50%. and tooth exfoliation. They stated that the chemical or physico- Since previous reports contraindicate the chemical interaction between the acrylic use of acrylic implants in man, we question resin and the tissue is the chief carcinogenic the advisability of using them in man until factor. Stinson23 reported that malignant long-term animal investigation has been changes occurred in the fibrous hyaline completed. capsule around large and medium sized acrylic disks when used in rats. Hueper24 References observed a difference in carcinogenecity be- 1. FLOHR, W.: L'Implantation de Resine au tween various water-soluble and water- Niveau de la Face et des Maxillaries Resul- insoluble polymers. However, it should be tats Cliniques et Histologiques, Rev Sto- noted that although the propensity of matol [Paris], 54:113, 1953. rodents to form short-term sarcomas, causes 2. HODOSH, M.; MONTAGNA, W.; POVAR, M.; and SHKLAR, G.: Implants of Acrylic Teeth one to be alert to the danger of acrylic in Human Beings and Experimental Ani- resins, it must not lead one to expect similar mals, Oral Surg 18:569-579, 1964. short-term results in man. Brown25 has sug- 3. HODOSH, M.; POVAR, M.; and SHKLAR, G.: gested that if it takes one year to develop a Attachment to the Plastic sarcoma in a rat, this time could be ex- Tooth Implant, J Periodontol 39:5-7, 1968. trapolated in man to 15 or 20 years. There- 4. HODOSH, M.; POVAR, M.; and SHKLAR, G.: fore, the advisability of using acrylic tooth The Dental Polymer Implant Concept, J implants in man is questionable until long- Prosthet Dent 22:371-380, 1969. 5. BROWN, B.H.; NEFF, P.A.; and TYLENDA, term animal investigation has been com- A.: Acrylic Resin Tooth Implants in Rhesus pleted. Monkeys. A Preliminary Report, J Prosthet The search for materials to repair or Dent 22:367-370, 1969. Vol 51 NO. 5 ACRYLIC RESTORATIONS & THE PERIODONTIUM 1387 6. WAERHAUG, J., and ZANDER, H.: Im- 16. ANDREASEN, J.O., and HJ0RTING-HANSEN, plantation of Acrylic Roots in Tooth E.: Replantation of Teeth. II. Histological Sockets, Oral Surg 9:46-54, 1956. Study of 22 Replanted Anterior Teeth in 7. NARANG, R., and WELLS, H.: Decalcified Human, Acta Odontol Scand 24:287-306, Allogenic Bone Enhances the Successful 1966. Maintenance of Implanted Acrylic Teeth, 17. LoE, H., and WAERHAUG, J.: Experimental abstracted, IADR Program and Abstracts of Replantation of Teeth in Dogs and Mon- Papers, No. 259, 1971. keys, Arch Oral Biol 3:176-184, 1961. 8. IWASCHENKO, G.M.: On the Possibility of 18. HAMMER, H.: Der Histologische Vorgang Implanting Acrylic Teeth and Roots, bei der Zahn-Replantation Nach Vernich- Stomatologiia (Mosk) 36:52-53, 1957. tung der Wurzelhaut, Dtsch Zahn Mund 9. TOBIN-WHITE, A.: Implantation of Acrylic Kieferheilkd, 4:179-187, 1937. Teeth in the , Int Dent J 8:15, 1958. 19. WAERHAUG, J., and LME, H.: Tissue Re- 10. CASTELLI, W.A.; NASJLETI, C.E.; HUELKE, action to Self-Curing Acrylic Resin Im- D.F.; and DIAZ-PEREZ, R.: Revasculariza- plants, Dent Pract Dent Res 8:234-240, tion of the Periodontium After Tooth 1958. Grafting in Monkeys, J Dent Res 50:414- 20. CSEREPFALVI, M.: Transplantation of Teeth 421, 1971. in the Human, in PEER, L.A. (ed): Trans- 11. KNIGHT, M.K.; GANS, B.J.; and CALANDRA, plantation of Tissues, vol. 2, Baltimore: J.C.: The Effect of Root Canal Therapy on Williams and Wilkins, 1959, p 301. Replanted Teeth of Dogs. A Gross, Roent- 21. ORBAN, B.: Pocket Elimination or Reat- genographic, and Histologic Study, Oral tachment, NY State Dent J 14:227, 1948. Surg 18:227-242, 1964. 22. OPPENHEIMER, B.S.; OPPENHEIMER, E.T.; 12. ROTHSCHILD, D.L.; GOODMAN, A.A.; and STOUT, A.P., WILLHITE, M.; and DANISHEF- BLAKEY, K.R.: A Histologic Study of Re- SKY, I.: The Latent Period in Carcinogenesis planted and Transplanted Endodontically by Plastics in Rats and Its Relation to the and Nonendodontically Treated Teeth in Presarcomatous Stage, Cancer 11:204-213, Dogs, Oral Surg 28:871-876, 1969. 1958. 13. DEEB, E.: Intentional Replantation of 23. STINSON, N.E.: The Tissue Reaction In- Endodontically Treated Teeth, in Transac- duced in Rats and Guinea Pigs by Poly- tions of the Fourth International Confer- methylmethacrylate (Acrylic) and Stain- ence on Endodontics, University of Penn- less Steel, Br J Exp Path 45:21-29, 1964. sylvania, 1968, pp 147-157. 24. HUEPER, W.C.: Carcinogenetic Studies on 14. BODECKER, C.F., and LEFKOWITZ, W.: Re- Water Soluble and Insoluble Macromole- plantation of Teeth, Dental Items 57:675- cules, Arch Path (Chicago) 67:587-617, 692, 1935. 1959. 15. HAMMER, H.: Der Histologische Vorgang 25. BROWN, D.E.: Tissue Reaction to Plastic bei der Zahn-Replantation Dtsch Kieferchir and Metal Implants, Arch Otolaryngol 88: 1:115-136, 1934. 283-287, 1968.